EXPLANATION OF THE TABLE.

The formula at the head of each series is a general expression for the atomic weights of that series. The names of the series are derived from the "Common Differences," which are the numbers multiplied by n in the general formulæ. In the columns headed "Theoretical" are given the atomic weights calculated from these formulæ and the values of n given in the last columns at the right of each division of the table. In the columns headed "Observed" will be found the observed values of the same atomic weights. These have been taken from the table of atomic weights given in the last volume of Liebig and Kopp's Jahresbericht (for 1852), with the exception of those against which are placed the initials of the observers. The last were taken from Weber's Alomgewichts Tabellen. In some cases the atomic weight is taken at twice its received value, but it is then underlined. The compounds in any one column at the right of the names of the elements are homologous. In the same way, those in any one at the left are isomorphous. The numbers at the head of these last columns indicate crystalline systems as follows: 1. Monometric; 2. Dimetric; 3. Trimetric; 4. Monoclinic; 5. Triclinic; 6. Hexagonal. The data from which the table was compiled were drawn from numerous sources, but especially from the following works: Gmelin's Handbook of Chemistry, Graham's Elements of Chemistry, Phillips's Mineralogy by Brooke and Miller, and Gustav Rose's Krystallo-chemische Mineralsystem. References have been given only in a few cases, to avoid crowding the tables. For authorities in other cases, the author would refer to the abovementioned works.

CORRESPONDence.

Extract from a letter from Dr. W. I. Burnett to Prof. J. D. Dana. Magnolia, Florida, March 1, 1854.

FLORIDA still remains almost a terra incognita to naturalists, although in geological structure, and Fauna and Flora, one of the most interesting States in the Union. Even from the limited survey I have made of its surface and general features, I am persuaded that some erroneous views have been entertained as to its formation and the exact nature of its peninsular relations. Naturalist after naturalist, from the time of the quaint old Bertram to the present day, have traversed its various sections, collecting specimens relating to their particular line of study, but no report has yet been made, [in full, of the

geological structure, the agricultural resources, or the Fauna and Flora of the state.*

Gen. Bernard's report of a survey by a corps of topographical engineers for a practical object, contains the greatest number of details, as well as the most reliable, upon the general features of Florida, that I have seen. In making these notes I shall draw somewhat from this report, especially as to measurements. From the southern boundaries of Georgia to a line drawn from Cape Canaveral to Tampa the land is cov. ered with pines, is much undulated, and in some places even hilly. The waters that run into the Atlantic Ocean and those that run into the Gulf of Mexico are divided by a ridge which extends slopingly from north to south, terminating at the above-mentioned line. The height of this ridge is certainly much greater than I had supposed, or than is generally understood even by those who have traversed the state, for the land rises very gradually and, without instruments, one is wholly deceived. The highest elevation is situated one mile west of Kinsley's pond and seven miles east of Sampson's pond, and is two hundred and thirty seven and one-half (237) feet above low tide in the Atlantic Ocean. There are other points on this ridge between 150 and 200 feet high; and, distant only a few miles west of St. John's river, I have traversed elevations, at least one hundred feet above the stream that encircled their base and ran towards the sea. I am particular thus to allude to this point in order to correct the erroneous opinion entertained by many that the whole peninsula of Florida is a flat sandy country, and not elevated more than fifteen feet any where above the level of the sea. The soil is sandy, but the hummocks contain red, yellow, or black clay, mixed with sand. The upper stratum is about six feet of sand, and the substratum appears to be limestone mixed with much sand. Scattered over the surface are more or less conical depressions or sinks. Those that I have seen are of pretty regular form, though of variable size; they contain no water, and are probably due to the substratum of limestone crumbling or being undermined from some cause. Nowhere so far as I am aware, do these depressions appear to be fed by intermittent springs, like those of the pine region of South Carolina, which have already been described by Mr. Tuomey.

In this connection, I may mention that Bernard's levelling parties commenced, one division at the Gulf of Mexico, the other at the Atlantic Ocean, and, proceeding inwards, met at Alapaka. At this point it was found that they were at an elevation of ninety-five feet above the level of low water of the Atlantic, and ninety-one and a half feet above the level of the low water of the Gulf-making three and a half feet difference between the low water level of these two waters. The same result was obtained by a repetition of this same levelling. The fact is quite interesting in connection with the phenomena of the Gulf Stream.

Buckingham Smith, Esq., is now engaged upon a detailed history of Florida, as I understand. The great pains he has taken to consult ancient documents relative to its primitive settlement, as well as his personal knowledge of the state physically, will ensure from him a most valuable work. But it is hoped that the legislature of this state will soon take measures for having a careful physical survey of Florida, by a competent geologist and naturalist.

But the physical features of the southern extremity of Florida are, as is well known, the most interesting. It is still land incompletely formed, and the conditions of its successive growth are yet visible. It is needless for me here to describe these conditions or to enter upon the details of this coral built promontory. Within a few years Agassiz has, as is well known, carefully studied not only the phases of the formation of the Keys, but also the coral-polyp marvels of the deep, which have led to these almost continental changes. Between the ridge above referred to and the everglades, is that remarkable collection of fresh water known as Lake Okechobee. Its average diameter is about thirty miles, and it is reputed to be quite deep. It contains a few islands, and is the reservoir of the neighboring streams, and of the Kissime river. South of this lake are the everglades which lie in a vast basin of limestone. They consist of a shallow lagoon-their wàters varying from one to six feet, studded with islets, trees, and a rank growth of vegetation. Their waters are fresh and due to the copious autumnal rains, and as the rim of the basin is some twelve or fifteen feet above the ocean, the slow moving currents set southwards towards the sea. This section of Florida, as shown by Agassiz in his recent lectures on the Florida reefs, is of coral origin and of comparatively modern date. Thus recently formed, the geology of this promontory may be easily inferred. It is oolitic limestone filled with the shells and corals, and the fossil remains of species that still exist. The present state of the Indian affairs did not allow me to visit this southerly point, but from intelligent gentlemen connected with the army, I learned that, besides the curious geological features I have above alluded to, this land presents many wonders and objects most interesting to the naturalist who will have the intrepidity and hardiness to explore it.

High up on the St. John's river there are from point to point vast de. posits of fluviatile shells. At Enterprise especially, these form even bluff-like elevations of forty to fifty feet, and of considerable extent. Hereabouts have been found also the fossil remains of Vertebrata that still exist. The whole physical structure of this region is of great geological interest, and would well repay the most careful examination.* One of the most interesting features of this State is the St. John's River. It furnishes a key to the whole plan of formation of a large portion of Florida. As is well known, its course is northward, unlike that of other American rivers, and this fact alone would indicate that the conditions of its primitive formation are different from those of other streams. It is in fact a chain of lakes, as its Indian name signifies, ( Welaka,) and it rises in the Cypress Swamp, situated near Indian River. Its similarity in appearance to an arm of the sea, is indeed more than apparent, for in its course of 300 miles, with often a width of six miles, there is a fall of only about twelve feet, and the tide is felt 100 miles above its mouth. But fed mostly by lateral infiltration chiefly on

*Our friend, Prof. Bailey, has been all about the travelled sections of Florida with his microscope, and his recently published results show that he had his eyes constantly and attentively upon the "invisible forms of life." He has also noticed, these grosser features (p. 23) which certainly are anything but microscopic. See Microscopical Observations made in South Carolina, Georgia and Florida, by J. W. Bailey, &c., &c. Smithsonian Contributions to Knowledge, vol. ii, Art. 8.

its western side, and receiving, besides, a few large tributaries, this majestic river, slow moving as it must be, discharges an enormous quantity of water into the sea. The segment of land included between its mouth and a line draw from its source to the sea, is at no point elevated above 12 or 14 feet, that is, higher than the fall of the river itself. It is therefore probable that this segment, like the whole southern extremity of the state, is of comparatively recent origin previous to which, of course, the St. John's River did not exist. This stream, consequently, is not properly a river, but rather an arm of the sea shut off from the ocean by alluvial sandy deposits. It receives the waters which arise on the easterly side of the ridge of the state, precisely as though it were the sea itself. Indian River presents the same phenomena, excepting that it is not wholly shut off from the ocean, but is open by inlets; and were it not for the influence of the Gulf Stream, the reef which forms its ocean boundary would be indefinitely extended until this river became truly an inland stream. By this view of the gradual geological changes that have supervened in this state, it would appear that ancient, primitive Florida, must have been of quite insignificant size, indeed, limited to the grand dividing ridge which perhaps is a spur of the upheavals of the states that bound it on the north-a narrow promontory thus extending southward from the main land, and only about half the length of the present peninsula. But the conditions of the formation of what may well be called modern Florida, have an additional interest from their relations to the phenomena of the Gulf Stream. Agassiz has shown that the coral building is now at an end on the southern extremity of this promontory, since the depth of the Gulf Stream as it shoots round this point is incompatible with the conditions of life of the coral polyp; and so all hope of an annexation, physical at least, of this continent to Cuba, is in vain. It is a curious question, What were the phenomena of this stream when ancient Florida alone existed? Is it possible that with a current anything like the present, the slow-growing coral-formation could have made progress to the extent we well know it really has ?

The Fauna and Flora of Florida seem much like those of Georgia and Alabama, as far as they go, for I have been surprised to find so great a deficiency in a land having so genial a climate. But this deficiency does not exist in one class-that of reptiles-at least, in the Saurians and Ophidians. The herpetologist will here find both venomous and nonvenomous snakes which will meet his desires both as to numbers and size; and that prince of American reptiles, the alligator, is here seen in an abundance that is almost incredible to any but the beholder. The natural history, the anatomy and physiology of this kingly Saurian has yet to be written, and a pleasant as well as a most honorable task remains for some American anatomist to monograph this subject, which he could easily do by placing himself for a season on some convenient spot on the St. John's river. Aside from the special anatomy of the animal, I am persuaded that careful, well-conducted physiological experiments, especially upon its nervous system, would furnish results of great value in physiology. Here the whole relations of the so-called reflex actions of the nervous system are presented upon a most magnificent scale.

The experiments that I have already made have proved deeply interesting to me, and have modified somewhat the opinions I have hitherto entertained upon this class of nervous actions. But this point will have my special consideration at another time.

I cannot close this letter without alluding to a subject which, among others has engaged my attention during my sojourn in Florida this winter for my health. I refer here to the orange insect or Coccus, which has almost entirely ruined the prospects of an occupation, one of the most delightful, as also one of the most profitable that man could here engage in-the culture of the orange. The climate and soil, especially of east and south Florida, is excellently fitted for the growth, almost to perfection, of this most delicious fruit. All along the St. John's river there are groves of the wild-orange that salute the eye most pleasantly, although this fruit is too acid to be palatable except when used to make a beverage (orangeade).

The China orange (Aurantium șinense) is the species which has here been introduced for cultivation as a commodity. Here it grows most luxuriantly, and, for size and flavor, has always had the preference in the market, even to those produced in more tropical regions. Some fifteen years since when the orange-culture of this state was in its most favorable condition, the revenue from this business was indeed wonderful: 6,500 oranges have been yielded by a single tree, 2,000 being a not uncommon yield. At a small place called Mandarin, situated on the St. Johns river, thirty-five miles from its mouth, there were annually produced 1,500,000 oranges. At other places, such as St. Augustine, there was a yield of even a greater number.

The cold of the winter of 1835 seriously affected the vitality and prosperity of the trees throughout the peninsula. But the great drawback now to their successful culture, is undoubtedly, the orange insect or Coccus. This insect appeared so as to be felt about the year 1838, and its increase and distribution since has worked most lamentable effects. Section after section has yielded to its ravages, and those fine groves above mentioned have become nearly ruined. The trees seem blasted, and only yield a very small quantity of fruit. Some of the groves I visited are now completely deserted; all hopes of an extermination of the pest being relinquished. Some trees that I examined seemed completely covered, trunk, limbs, leaves, and fruit, with this insect, and it is not at all strange that the vitality of the trees yields to such a draft upon its juices.

Careful, from scientific reasons, not to lose so excellent an opportu nity for the study of the animal, and desirous, from practical reasons, to find out, if possible, a means for its extermination,-this insect has received no little attention from me. It is exceedingly small and insig. nificant for so disastrous a worker, the males being only and the females about of an inch in length. On this account, its anatomy and physiology could be successfully studied only by the microscope; but the results afforded have well repaid the labor thus bestowed. These results are certainly sufficiently important for a special consider. ation, which I propose to give them, at some future time. It will suf fice for me to say here, that the conditions of their reproduction are remarkable, and quite favorable for the prodigious multiplicity of this